Process for the preparation of perhaloalkanoyl chloride

ABSTRACT

A process for the preparation of perhaloalkanoyl chloride is disclosed which comprises reacting 1,1,1-trichloroperfluoroalkane, with a sulfur trioxide-containing compound selected from the group consisting of oleum sulfur trioxide and stabilized sulfur trioxide in the presence of catalytic amounts of a halogen catalyst selected from the group consisting of iodine, bromine, iodine monobromide and iodine monochloride and bromine monochloride. The preferred product is trifluoroacetyl chloride.

DESCRIPTION BACKGROUND OF THE INVENTION

The present invention relates to preparation of perhaloalkanoyl chloride by contacting 1,1,1-trichloroperhaloalkanes with a SO₃ -containing substance in the presence of a catalytic amount of a halogen catalyst. More particularly, the present invention relates to the preparation of trifluoroacetyl chloride by contacting 1,1,1-trichloro-2,2,2-trifluoroethane with SO₃ -containing substance in the presence of selected halogen catalyst, such as bromine.

Perhalo compounds wherein the halogen is chlorine or fluorine are particularly resistant to oxidizing agents.

Specifically, trifluoroacetyl chloride, CF₃ COCl, a known chemical compound having a boiling point of -19° C., is a valuable chemical intermediate, useful for the preparation of trifluoroethanol, trifluoroacetic acid, and trifluoroacetaldehyde. Trifluoroethanol, further is a raw material useful in the manufacture of novel anesthetic compounds. Perhaloalkanoic acids, such as trifluoroacetic acid is also an intermediate for the preparation of compounds useful as herbicides, insecticides, dyes, etc. Higher homologous perhaloalkanoyl chlorides, for example perfluorooctanoyl chloride, CF₃ (CF₂)₆ COCl is easily converted to the carboxylic acid or acid salt which is useful as an surfactant.

In the relevant prior art procedures, trifluoroacetyl chloride has been prepared by the catalytic hydrolysis of 1,1,1-trifluoro-2,2,2-trichloroethane, using oleum, (sulfur trioxide dissolved in sulfuric acid), in the presence of toxic mercurial salt catalysts. These prior art procedures are described, particularly in Lawlor and Braid: U.S. Pat. No. 3,102,139; Dittman and Zager: U.S. Pat. No. 3,160,659; and Pauchsch et al.: U.S. Pat. No. 3,725,475.

Trifluoroacetyl chloride has also been previously prepared by subjecting a mixture of chlorine, oxygen and 1,1,1-trifluoro-2,2,2-trichloroethane to ultraviolet irradiation under anhydrous conditions, as described by Braid and Lawlor in U.S. Pat. No. 3,151,051.

In general, methods described in the prior art for the preparation of perhaloalkanoyl compounds have required excessively prolonged reaction times, elevated reaction pressures, hazardous ultraviolet radiation, and have generally resulted only in low yields of the desired end products, frequently accompanied by losses of starting materials due to side reactions such as carbon-to-carbon bond cleavage. In addition, the prior art preparations discussed above have also been characterized by the need to use toxic mercurial salt catalysts, which require costly environmental pollution control systems, and which create difficult environmental waste disposal problems, particularly associated with the safe disposal of by-product sulfuryl chloride-containing mercurial salts.

Thus, a process for the preparation of perhaloalkanoyl chloride from 1,1,1-trichloroperhaloalkane using a nonmetallic, nonpolluting, and low cost halogen catalyst, has significant commercial and technical value.

Accordingly it is an object of the present invention to provide a process for the preparation of perhaloalkanoyl chloride in the presence of a halogen catalyst which is non-metallic and which embodies none of the operating and environmental disadvantages of the prior art procedures.

Another object of the present invention is to provide a process for the preparation of high purity trifluoroacetyl chloride in a simple and efficient manner, and in high yield.

SUMMARY OF THE INVENTION

In accordance with the objects of the present invention, there is provided a process for the preparation of perhaloalkanoyl chloride which comprises contacting 1,1,1-trichloroperhaloalkane with an effective amount of a sulfur trioxide-containing substance selected from the group consisting of oleum, SO₃ and stabilized SO₃ in the presence of a catalytic amount of a halogen catalyst. There is further provided a process for preparation of trifluoroacetyl chloride, which comprises contacting 1,1,1-trichloro-2,2,2-trifluoroethane with a sulfur trioxide-containing substance selected from the group consisting of oleum, SO₃ and stabilized SO₃ in a molar range of from about 1:1 to about 1:10, and in the presence of from about 0.5 to about 10 percent by weight of a halogen catalyst, based on the weight of the 1,1,1-trichloro-2,2,2-trifluoroethane.

DETAILED DESCRIPTION OF THE PRESENT INVENTION AND OF THE PREFERRED EMBODIMENTS

The present invention employs a catalytic amount of a non-metallic, halogen catalyst for the contact of 1,1,1-trichloroperhaloalkane with a sulfur trioxide containing substance for a time sufficient to effect conversion thereof to perhaloalkanoyl chloride. While toxic mercurial salts catalysts were disclosed in the U.S. Pat. No. 3,102,139, the halogen catalyst of the present invention is a member selected from the group consisting of iodine, bromine, iodine monochloride, iodine monobromide and bromine monochloride. Bromine is the preferred halogen catalyst. The catalytic amount of the halogen catalyst is in the range of from about 0.5% to about 10% by weight of 1,1,1-trichloroperhaloalkane. An upper limit on the catalytic amount of halogen catalyst has not been found to be critical; an amount of halogen catalyst as low as about 0.5% by weight of 1,1,1-trichloroperhaloalkane had been found effective. Only economic consideration would preclude employing catalytic amount of halogen catalyst in excess of about 10% by weight of 1,1,1-trichloroperhaloalkane.

The 1,1,1-trichloroperhaloalkane found useful in the present invention is a straight or branched-chain acyclic organic compound having 2 to 8 carbon atoms and having at least two trihalomethyl groups, with one trihalomethyl being 1,1,1-trichloromethyl and with the other trihalomethyl having at least one fluorine. Exemplary of the useful organic compounds are ##STR1## or F. While the trichloroperhaloalkanes may contain halogens such as chlorine at carbons other than the one carbon, for example CF₂ Cl--CCl₃ (See Example IV) and CF₂ ClCFCl--CCl₃ (See Example VI), substantially complete fluorine substitution at carbons other than carbon one is preferred; CF₃ (CF₂)₆ CCl₃ and CF₃ CCl₃ are especially preferred.

The sulfur trioxide-containing substance useful in the present invention is a member selected from the group consisting of oleum, gaseous or liquid sulfur trioxide and stabilized liquid sulfur trioxide. Oleum is sulfuric acid with an amount of sulfur trioxide varying from a trace (so called fuming sulfuric acid) to 100% sulfur trioxide. Small amounts of compounds such as trimethoxy boraxime can conveniently added to stabilize sulfur trioxide in the liquid form and prevent polymerization thereof to a solid. Stabilized liquid sulfur trioxide is the preferred sulfur trioxide containing substances. The amount of the sulfur trioxide-containing substance employed in the present invention is from about 1 mole to about 10 moles, preferably about 2 moles of sulfur trioxide per one mole of 1,1,1-trichloroperhaloalkane. Only economic considerations preclude employing more than 10 moles of sulfur trioxide per one mole of 1,1,1-trichloroperhaloalkane.

Operating temperatures and pressures for the preparation of perhaloalkanyl chloride are not critical. While operating temperatures in the range of about 20° to about 100° C. at pressures of about one atmosphere, plus or minus about 0.1 to 0.5 atmospheres have been found effective, as a matter of operating convenience temperatures in the range of about 25° to about 60° C. at a pressure of about one atmosphere are preferred.

Exact contact times are not critical. Preferred contact times vary between about 5 hours and about 24 hours for batch production of trifluoroacetylchloride; longer contact times result in higher percent conversion of 1,1,1-trichloroperhaloalkane to perhaloalkanoyl chloride. However, for continuous production, it is desirable to contact, in the temperature range of from about 20° to about 100° C., preferably from about 25° and 60° C. at about one atmosphere of pressure, 1,1,1-trichloroperhaloalkane with an effective amount of a sulfur trioxide-containing substance, preferably stabilized liquid sulfur trioxide in the presence of a catalytic amount of a halogen catalyst, preferably bromine, preferably in an amount of about 1% by weight of 1,1,1-trichloroperhaloalkane.

A cold trap provided on a reactor of any convenient design will allow collection of volatiles escaping from the contacting of the present invention. The perhaloalkanoyl chloride can conveniently be fractionally distilled. In a preferred embodiment, condensed volatiles from the contacting of 1,1,1-trichloro-2,2,2-trifluoroethane with SO₃ in the presence of Br₂ have been fractionally distilled for recovery of substantially pure, i.e., almost 100% pure, trifluoroacetyl chloride. The chemicals remaining in the reactor have also been fractionally distilled; starting materials, 1,1,1-trichloro-2,2,2-trifluoroethane, sulfur trioxide and halogen catalyst, i.e., bromine can conveniently be recycled for subsequent preparation of trifluoroacetyl chloride. Pyrosulfurylchloride, S₂ O₅ Cl₂, a by-product, can also be recycled as a convenient diluent.

The process of the invention will be further described and illustrated by the following specific examples.

GENERAL EXPERIMENTAL

1,1,1-trichloroperhaloalkanes are conveniently prepared by methods described in literature. See for example U.S. Pat. No. 3,102,139 which is hereby incorporated by reference. 1,1,1-trichloro-2,2,2-trifluoroethane is prepared in accordance with the following reactions: ##STR2## CF₂ ClCFCl CCl₃ is prepared by addition of CCl₄ to CF₂ ═CFCl using AlCl₃ catalyst. 1,1,1-trichloroperhaloalkane having an even number of carbons, such as CF₃ (CF₂)₂ CCl₃ is prepared by reaction of a symmetrical ether, such as (n-C₄ F₉)₂ O with AlCl₃ in an autoclave at 175° to 230° C. The trichloroperhaloalkane having an odd number of carbons, such as CF₃ (CF₂)₃ CCl₃ is prepared by reaction of an unsymmetrical ether, such as CF₃ (CF₂)₃ OCF₂ CF₃ with AlCl₃ in an autoclave reaction at elevated temperatures.

EXAMPLE I

Into a 250 ml, 3-neck reaction flask equipped with a thermometer, magnetic stirring bar, dropping funnel and a water-cooled condenser, topped by a dry ice condenser maintained at -15° C. and connected to Dry Ice trap, cooled to -78° C., were charged 150 g (0.80 mole) of trifluorotrichloroethane (CF₃ CCl₃) and 7.5 g bromine. At room temperature, 145 g (1.82 moles) of SO₃ were added over a half-hour period. The reaction mixture was heated from 25° C. to 60° C. over a twelve hour period. Fractional distillation of the cold trap product, (102.8 g), effected recovery of 85 g (0.64 mole) of trifluoroacetyl chloride (CF₃ COCl), bp -19° C. Distillation of the material remaining in the reaction flask showed the presence of 20 g (0.15 mole) CF₃ CCl₃, bp 46° C. and 110 g (0.52 mole) S₂ O₅ Cl₂, bp 153° C., as well as unreacted SO₃ and bromine catalyst. Thus of the starting material fed 80% was converted to CF₃ COCl. The yield based on starting material consumed was 98%. The IR spectrum of the recovered trifluoroacetyl chloride was consistent with the expected structure.

EXAMPLE II

In the test apparatus as described in Example I, and following the procedure of Example I, 37.5 g (0.20 mole) of CF₃ CCl₃, 100 g 65% oleum (0.80 mole as SO₃) and 3 g iodine were heated to reflux for 48 hours. Fractional distillation of the cold trap product, 19.3 g, effected recovery of 15.2 g (0.114 mole) of CF₃ COCl for a 57.3% conversion. The yield based on recovery of 13 g (0.07 mole) CF₃ CCl₃ starting material was 87%.

EXAMPLE III

In the test apparatus as described in Example I, and following the procedure of Example I, 37.5 g (0.20 mole) CF₃ CCl₃, 100 g 65% oleum (0.80 mole as SO₃) and 3 g iodine monochloride were heated to reflux for 24 hours. Fractional distillation of the cold trap product, 15 g, effected recovery of 12 g (0.09 mole) of CF₃ COCl for a 45% conversion. The yield based on recovery of 16 g (0.085 mole) of CF₃ CCl₃ starting material was 78%.

EXAMPLE IV

In the test apparatus as described in Example I, and following the procedure of Example I, 150 g (0.74 mole) of CF₂ ClCCl₃, 200 g 65% oleum (1.60 moles as SO₃) and 7.5 g bromine were heated from 25° C. to 60° C. over a 5 hour period. Fractional distillation of the cold trap product, 90 g, gave 77 g (0.375 mole) of CF₂ ClCOCl, bp 26° C., for a 51% conversion.

EXAMPLE V

In the test apparatus as described in Example I, and following the procedure of Example I, 75 g (0.315 mole) of CF₃ CF₂ CCl₃, 100 g 65% oleum (0.80 mole as SO₃) and 5 g bromine were heated from 25° C. to 60° C. over a 5 hour period. Fractional distillation of the cold trap product, 50 g, gave 42 g (0.23 mole) of CF₃ CF₂ COCl, bp 9° C., for a 73% conversion.

EXAMPLE VI

In the test apparatus as described in Example I, and following the procedure of Example I, 135 g (0.50 mole) of CF₂ ClCFClCCl₃, 150 g 65% oleum (1.20 moles as SO₃) and 10 g bromine were heated from 25° C. to 60° C. over a 5 hour period. Fractional distillation of the product gave 90 g (0.42 mole) CF₂ ClCFClCOCl for an 84% conversion.

EXAMPLES VII-XXX

In the following examples the process of Example I is repeated in the apparatus as described except that the 1,1,1-trichloroperfluoroalkane reactant and catalyst are varied as indicated in the following table.

                  TABLE                                                            ______________________________________                                                1,1,1-trichloro-                                                                              Cata-                                                    Example                                                                               perhaloalkane  lyst    Product                                          ______________________________________                                         VII    CF.sub.3 (CF.sub.2).sub.2 CCl.sub.3                                                           Br.sub.2                                                                               CF.sub.3 (CF.sub.2).sub.2 COCl                   VIII   "              I.sub.2 "                                                IX     "              ICl     "                                                X      "              IBr     "                                                XI     "              BrCl    "                                                XII    (CF.sub.3).sub.2 CF(CF.sub.2).sub.2 CCl.sub.3                                                 Br.sub.2                                                                               (CF.sub.3).sub.2 CF(CF.sub.2).sub.2 COCl         XIII   "              I.sub.2 "                                                XIV    "              ICl     "                                                XV     "              IBr     "                                                XVI    "              BrCl    "                                                XVII   CF.sub.3 (CF.sub.2).sub.5 CCl.sub.3                                                           Br.sub.2                                                                               CF.sub.3 (CF.sub.2).sub.5 COCl                   XVIII  "              ICl     "                                                XIX    "              IBr     "                                                XX     "              BrCl    "                                                XXI    CF.sub.3 (CF.sub.2).sub.6 CCl.sub.3                                                           Br.sub.2                                                                               CF.sub.3 (CF.sub.2).sub.6 COCl                   XXII   "              I.sub.2 "                                                XXIII  "              ICl     "                                                XXIV   "              IBr     "                                                XXV    "              BrCl    "                                                XXVI   FCCl.sub.2 (CFCl).sub.6 CCl.sub.3                                                             Br.sub.2                                                                               FCCl.sub.2 (CFCl).sub. 6 COCl                    XXVII  "              I.sub.2 "                                                XXVIII "              ICl     "                                                XXIX   "              IBr     "                                                XXX    "              BrCl    "                                                ______________________________________                                    

Although certain preferred embodiments of the present invention have been disclosed, for the purposes of illustration, it will be readily evident to one skilled in the art that various changes and modifications may be made therein without departing from the scope and spirit of the invention. 

We claim:
 1. A process for preparation of perhaloalkanoyl chloride, which comprises contacting a 1,1,1-trichloroperhaloalkane with an effective amount of a sulfur trioxide-containing substance selected from the group consisting of oleum, SO₃ and stabilized SO₃ in the presence of a catalytic amount of a halogen catalyst, wherein the 1,1,1-trichloroperhaloalkane is a straight or branched chain acyclic organic compound having 2 to 8 carbon atoms and having at least one trihalomethyl group wherein at least one halo atom is fluorine, having the remaining carbon atoms substituted by chlorine or fluorine atoms.
 2. The process of claim 1 wherein the halogen catalyst is a member selected from the group consisting of iodine, bromine, iodine monochloride, iodine monobromide and bromine monochloride.
 3. The process of claim 1, wherein the halogen catalyst is iodine.
 4. The process of claim 1, wherein the halogen catalyst is bromine.
 5. The process of claim 1, wherein the halogen catalyst is iodine monochloride.
 6. The process of claim 1, wherein the halogen catalyst is iodine monobromide.
 7. The process of claim 1, wherein the halogen catalyst is bromine monochloride.
 8. The process of claim 1 wherein the effective amount of the sulfur trioxide-containing substance contains from about one mole to about ten moles of sulfur trioxide to about one mole of 1,1,1-trichloroperhaloalkane.
 9. The process of claim 1, wherein the catalytic amount of the halogen catalyst is in the range of about 0.5% to about 10% by weight of the 1,1,1-trichloroperhaloalkane.
 10. The process of claims 1, 8 or 9 wherein the perhaloalkane is 1,1,1-trichloro-2,2,2-trifluoroethane.
 11. The process of claims 1, 8 or 9 wherein the perhaloalkane is 1,1,1-trichloroperfluorooctane.
 12. A process for preparation of trifluoroacetyl chloride, which comprises contacting, in the temperature range of from about 20° to about 100° C., 1,1,1-trichloro-2,2,2-trifluoroethane with sulfur trioxide-containing substance selected from the group consisting of oleum, SO₃ and stabilized SO₃ in a molar ratio of the trichlorotrifluoroethane to sulfur trioxide of from about 1:1 to about 1:10, in the presence of from about 0.5 to about 10 percent by weight of a halogen catalyst based on the weight of the 1,1,1-trichloro-2,2,2-trifluoroethane.
 13. The process as described in claim 12 wherein said molar ratio is 2:1 and said temperature is in the range of from about 25° to about 60° C.
 14. The process as described in claim 12 or 13 wherein the halogen catalyst is bromine. 